The objective is to assemble a multi-state data file of infant deaths in which prior linkage with birth certificate information has been performed. The studies to be done on the data set include associations between infant and fetal mortality with the standard information on birth certificates (e.g. birthweight, gestational age, maternal age and race, parity, etc.). These studies will be compared with similar studies on a 1950 and 1960 cohort of U.S. births. Additional comparisons will be made to linked data from Canada (1971), Great Britain (1970), Norway (1967-1976), and Sweden (1975-1978).